The present invention is a regenerative type valve, also referred to as a speed-up valve, which increases the speed of extension of a double-acting hydraulic cylinder by directing the discharge flow from the rod end of the cylinder into the opposite head end of the cylinder along with pressurized pump flow.
This speed-up movement is normally desired in a light load or low load condition, as for example, dumping a bucket. Functions of this nature are normally the return stroke after a working condition and any time interval which can be saved has a direct effect upon the working capacity of the machine.
Many valve arrangements and circuits for regeneration in double-acting cylinders are known in the prior art. One type of such a valve which includes a single shuttle spool is illustrated in U.S. Pat. Nos. 2,890,683 and 2,590,454. One problem with the last-mentioned single spool type valve is that under a heavy load condition the valve will not function in shifting to its regenerative position. In order to solve this problem, more complex valves have been designed which utilize a combination of separate check valves and shuttle spools, the type of which is illustrated in U.S. Pat. Nos. 4,194,436 and 3,568,707.
The next stage of development for regeneration valves from the compound type valve last mentioned, is the valve design which combines the shuttle spool and check valve into a single bore with the movement of the shuttle spool also functioning to open the check valve for reverse flow.